Vacuum table system for printing machine



United States Patent [72] Inventors Matthew L. Jalfa 92 Clark St.,Rutherford, New Jersey 07070; David Jana, 38-26 Allvvood Place,Fairlawn, New Jersey 07410 [21] Appl. No. 734,991 [22] Filed June 6,1968[45] Patented Sept. 8, I970 [54] VACUUM TABLE SYSTEM FOR PRINTINGMACHINE 9 Claims, 3 Drawing Figs.

[52] U.S.Cl 101/407, 101/126 [51] lnt.Cl B41fl/32, B4lf 15/20 [50]FieldofSearch 101/123, 124,407, l27.l,4l5;271/74, 12,26; 226/95;248/362, 363; 267/21; 101/126 [56] References Cited UNITED STATESPATENTS 1,288,607 12/1918 Jobke 248/363 SOURCE Morganstern et a1 .laffaet a1.

ABSTRACT: A multiple-suction area vacuum table system for use with aprinting machine to hold sheet material to be printed against a porous,endless conveyor belt that carries the sheets from a feed station to aprinting station and thence to a collection station. The vacuum levelsof the suction areas are independently adjustable and are controlled inaccordance with the movements of the belt and the printing head so thatwhen the belt is indexed, the vacuum level along the table length issufficient to hold the sheets flat against the belt without imposing anexcessive suction drag thereon, and dur' ing the printing operation thevacuum level at the printing station is raised to more firmly grip thesheet being printed so as to prevent any rippling thereof by the actionof the squeegee associated with the printing head.

Patented Sept. 8, 1970 3,527,166

'1 N VENTOR.

lAtCUlUM TABLE SYSTEM FOR PRINTING MACHINE BACKGROUND AND SUMMARY OF THEINVENTION This invention relates in general to printing machinery whichemploy vacuum conveyor belts and more particularly to a vacuum tablesystem for holding sheet material against the conveyor belt.

in typical vacuum belt printing machinery installations, the sheetmaterial to be printed is laid upon the belt at a feed station and iscarried thereby to a printing station whereat the printing operation isperformed, and then the printed sheet is carried by the belt to acollection station to be discharged thereat. Ordinarily an endless beltis used, and the belt moves intermittently such that each time the beltis indexed, a blank sheet at the feed station is brought to the printingstation and underneath the printing head, and the sheet that was lastprinted is advanced from the printing station toward the collectionstation by an equivalent distance. At the end of each indexing movement,the belt is stopped momentarily and the printing head is brought downtoward the belt to print the sheet that has arrived at the printingstation. After the printing operation is completed, the printing head israised and the belt is re-indexed to bring up a new sheet. This sequenceof belt indexing and printing head motions is repeated as often asnecessary to print the desired number of sheets.

It is important that the sheet at the printing station be held flat andsecurely to prevent any rippling during the printing operation by theaction of the squeegee associated with the printing head. In the priorart, holding of the sheet at the printing station has been accomplishedby vacuum forces provided by a vacuum table underlying the belt. Suchvacuum table is ordinarily an evacuable chamber that extends lengthwisealong the conveyance path for a distance somewhat greater than the sheetlength, and extends transversely to the conveyance path for a distanceapproximately equal to the belt width, and has one or more openingsexposed to contact the inner side of the belt. The belt is porous orperforated such that the vacuum table openings establish correspondingsuction areas along the outer side ofthe belt sections passing over theopenings. Thus, each sheet brought to the printing station will begripped at these suction areas and will be held flat against the belt soas not to ripple or slip during the printing operation.

The vacuum pressure level required for sheet holding during the printingoperation would, if applied to the area of the belt outside the printingstation area, such as over that portion of the belt between the feedstation and the printing station, have imposed a high suction drag loadupon the belt which would give difficulties in indexing it.Consequently, with a vacuum table that could only have a singleevacuation pres sure level, which had to be high enough for the printingoperation requirements, extension of the table from the printing stationarea to the feed station so as to provide vacuum gripping of sheetsconveyed therebetween was for all practical purposes prohibited.

Since it is also necessary that the sheets conveyed from the feedstation to the printing station be held flat and firmly against the beltin order to arrive at the printing station in proper registry with theprinting head, it was necessary to provide mechanical grippers or clampsmounted to the belt for movement therewith. Such gripping clamps werenormally mounted on both edges of the belt thereby reducing theavailable Width of sheet that could be handled, and also reducing thewidth of the pattern which could be printed on the sheets that werehandled. Because out. the central width portions of the sheets could beprinted. the outer width portions held by the clamps were left blank,and in cases where such blank portions were undesired in the finishedproduct, the printed sheets had to be trimmed.

The invention provides a vacuum table system that dispenses with theneed for any mechanical clamps on the belt and instead uses a multiplevacuum zone type vacuum table in which the vacuum gripping forces onsheets being conveyed from the feed station to the printing station canbe adjusted without affecting the gripping forces applied to the sheetof the printing station during the printing operation, and vice versa.

In the system of the invention, the vacuum table is positioned forcontact with the inner side of the porous belt to support it along thepath of conveyance, at least from the beginning of the feed station tothe end of the printing station, and the table has partition meansdefining a plurality of evacuable spaces open to the inner side of thebelt to establish corresponding suction areas along the outer side ofthe belt for gripping the sheet material conveyed thereby. Passage meansare provided for communicating selected groups of these spaces with oneanother so as to allow evacuation of all spaces in each group to a givenpressure independently of the pressure to which the spaces of any othergroup are evacuated. Thus the gripping force exerted on the sheetmaterial conveyed through the suction areas associated with said spacescan be adjusted by correspondingly adjusting the evacuation pressures ofindividual groups of spaces.

According to a preferred embodiment of the invention there is providedon the table a first group of evacuable spaces establishing suctionareas located between the feed station and the beginning of the printingstation, and a second group of evacuable spaces establishing suctionareas located between the printing station and the collection stationand distributed throughout substantially the entire printing area at theprinting station.

By controlling the vacuum in the first group of spaces, it is possibleto regulate the gripping force on sheets conveyed from the feed stationto the printing station so that they are held flat and do not slip outof registry. Likewise by controlling the vacuum in the second group ofspaces, the gripping force on the sheet at the printing station can beset to prevent any slippage during the printing operation. Since thevacuum levels of the two groups of spaces can be independentlycontrolled it is possible to hold the two groups of spaces at a reducedvacuum level during the feeding mode of opera tion to reduce the suctiondrag when indexing the belt, and then during the printing operation, toraise the vacuum level of the second group of spaces and either hold thefirst group of spaces at the reduced vacuum, or vent them to theatmosphere.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification.

For a better understanding of the invention, its operating advantagesand specific objects attained by its use, reference should be had to theaccompanying drawing and descriptive matter in which is illustrated anddescribed a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic elevation view, partly in section of a vacuumtable system according to a preferred embodiment of the invention andillustrating its use in connection with a typical vacuum belt printingmachine.

FIG. 2 is a plan view of the vacuum table used in the vacuum tablesystem of FIG. 1.

FIG. 3 is a sectional elevation view of the vacuum table shown in FIG. 2as taken along line 3-3 therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In FIG. 1there is illustrated a vacuum belt type printing apparatus 10 whereinsheets of paper or other material to be printed are laid upon an endlessporous conveyor belt 11 at a feed station 12 and are carried thereby toa printing station 13 where they are contacted by a printing head 14 andprinted thereby. After the printing operation is performed on any givensheet, it is carried by belt 11 to a collection station 15 where it isejected or otherwise removed from the belt 11.

The belt 11 moves intermittently rather than continuously such that thefirst sheet in a sequence of similar sheets to be printed is laid on thebelt 11, and the belt 11 is indexed in the forward direction, asindicated by arrow 16, by the distance required to bring the sheet toprinting station 13, under printing head 14 and in registry therewith.Printing head 14 moves up and down with respect to belt 11 and insynchronism with the indexing motion thereof such that printing head 14is in a raised position when the sheet begins to move from the feedstation 12, and remains raised until the sheet arrives in the printingregistry position at station 13. This assures that there will not be anyinterference by the printing head 14 with the movement of the sheets tobe printed or that have been just printed. Upon arrival of the sheet atthe printing station 13, belt 11 is halted and printing head 14 islowered into contact with the sheet, as shown in dotted outline form, toperform the printing operation. After the sheet has been printed, theprinting head 14 is raised and belt 11 is re-indexed to print the nextblank sheet up to printing station 13 and to simultaneously advance thejust printed sheet toward collection station 15. The foregoing basicindexing and printing head motions can be repeated as often as necessaryto print any selected number of consecutive sheets.

It can therefore be noted that the printing apparatus has two basicstates, or modes of operation, one being the indexing mode characterizedby the fact that printing head 14 is raised and belt 11 is moving, andthe other being the printing mode characterized by the fact thatprinting head 14 is lowered and belt 11 is halted. These two operatingmodes are readily detectable by any one ofa variety of monitoring meansthat can be used in accordance with the invention to control theoperation of a vacuum table system associated with printing apparatus10.

Vacuum table system 20 includes a vacuum table 21 shown in greaterdetail by FIGS. 2 and 3. The vacuum table 21 is made up of an air tighthollow box 22 subdivided by an air tight barrier 23 into two plenumchambers 24 and 25 which are covered top and bottom by sealing panels 26and 27 respectively. On the top sealing panel 26 is provided a layer ofepoxy 19 which acts as a bed for a plate 28. Plate 28 is made up of aplurality of adjoining coplanar grooved or ribbed sections 28A, 28B,arranged in underlying relation to the porous belt 11 and for contactwith the inner side thereof to support belt 11 along the path ofconveyance from the beginning of feed station 12 up to at least the endof the printing area 29 of printing station 13. Recessed into the upperside of plate 28 are a first set of extended parallel grooves 30A and asecond set of longitudinally extending parallel grooves 308. Grooves 30Aextend from the beginning of feed station 12 up to approximately thebeginning of the printing station 13. and grooves 308 extend from thebeginning of printing station 13 up to the end of the printing area 31associated therewith. Grooves 30A and 30B are prevented from runninginto one another by a barrier section 32 of plate 28 extending acrossthe width thereof at the beginning of printing station 13. Grooves 30Aare stopped at their feed station 12 end by a barrier section 33 ofplate 28, and are spaced apart by intervening barrier sections 34A ofplate 28. At the end of the printing area 31, the grooves 30B arestopped by a barrier section 35 of plate 28, and are spaced apart byintervening barrier sections 348 ofplate 28.

Grooves 30A are communicated with plenum chamber 24 and therebycommunicated with one another by means of passages 36A drilled throughplate 28, epoxy layer 19 and panel 26. Likewise, grooves 303 arecommunicated with plenum chamber 25, and thereby communicated with oneanother by means of similar passages 36B drilled through plate 28, epoxylayer 19 and panel 26.

The plenum chambers 25 and 24 are evacuable independently of each other,and hence the grooves 30A will all have the same evacuation pressure asplenum chamber 24 whereas the grooves 308 will all have the sameevacuation pressure as plenum chamber 25.

The barrier sections 32, 33, 34A, 34B and 35 can be considered aspartition means defining a plurality of evacuable spaces, i.e. grooves30A and 308 open to the inner side of belt 11 and when evacuatedestablish corresponding suction areas along the outer side of belt 11for gripping the sheet material conveyed thereby.

To adjust the gripping force on sheets conveyed from feed station 12 toprinting station 13 and passing through the suction areas established bygrooves 308 it is only necessary to adjust the vacuum pressure withinplenum chamber 24, and likewise to adjust the gripping force on sheetsconveyed into the printing area 31, the vacuum pressure within plenumchamber 25 is adjusted.

In the operation of printing apparatus 10, it is desirable to hold thegrooves 30A and 308 at substantially the same vacuum pressure levelduring the feeding mode of operation so that sheets conveyed from thefeed station 12 to printing station 13 will be held flat against thebelt 11 with a vacuum gripping force distributed across the width ofbelt 11 sufficient to prevent sheet slippage, but not so great as toimpose a suction drag upon belt 11 that might overload the motor means(not shown) that effects the belt indexing motion.

During the printing operation, a somewhat higher vacuum gripping forceis needed to securely grip the sheet at the printing station 13 againstany slippage due to the wiping action of the squeegee (not shown)associated with printing head 14. The vacuum gripping force over theportion of the belt between the feed station 12 and printing station 13need not be maintained during the printing operation since the belt 11is stationary.

The regulation of the vacuum pressures of grooves 30A and 30B isaccomplished by means ofa vacuum control regulation circuit 40 in whichthe inlet of a first solenoid valve 41 is communicated with plenumchamber 24 by a line 42 and the outlet of valve 41 is communicated withone branch of a four-way cross connection fitting 43 by a line 44.Plenum chamber 25 is communicated with another branch of fitting 43 by aline 46, as is the inlet of a second solenoid valve 47 and one side of ableeder valve 48. The other side of valve 48 and the outlet of valve 47are both communicated with a vacuum source 49 via a T-fitting 50.

Valve 41 is open during the feeding mode of operation whereas valve 47is closed so as to establish a vacuum pressure equalizing flowconnection between the plenum chambers 24 and 25 for equalizing thevacuum pressures in both sets of grooves 30A and 30B. In addition,during the feeding mode, valves 41 and 47 are in states which establisha flow connection through bleeder valve 48 between the vacuum source 49and both plenum chambers 24 and 25. Consequently, both sets of grooves30A and 308 will be at a uniform pressure level established by bleedervalve 48 during the feeding mode.

During the printing mode of operation, valve 41 is closed and valve 47opened. This cuts off the vacuum in plenum chamber 24 and establishes aflow connection between plenum chamber 25 and the vacuum source 49bypassing bleeder valve 48. Thus, in the printing mode, the full vacuumpressure of source 49 will be applied to the grooves 308 whereas vacuumto the grooves 30A will be cutoff. If desired, the valve 41 can be onewhich when closed will vent plenum chamber 24 and the grooves 30A to theambient atmosphere.

The operation of solenoid valves 41 and 47 is coordinated with theoperation of the printing apparatus 10 by a monitoring means that iscapable of sensing whether the apparatus 10 is in its feeding mode orits printing mode and establishing a corresponding feeding or printingcondition indicator signal accordingly. Such monitoring means can be inthe form of a switch 60 that senses the position of printing head 14 andeither opens or closes to establish a printing condition indicatorsignal whenever the printing head 14 is in the down position it normallyassumes when performing the printing operation. By using a solenoidvalve 41 which is normally open when its operating solenoid isde-energized, and a solenoid valve 47 which is normally closed when itsoperating solenoid is de-energized, the operating solenoids of bothvalves 4ll and 47 can be conveniently connected together electrically inparallel. For example, with a monitoring switch 60 that is open whenprinting head 14 is raised, as during the feeding mode, and closed whenprinting head 14 is lowered, as during the printing mode, switch 60 canbe connected in series with an electrical voltage source 61 and theoperating solenoids of valves 41 and 47 to provide at such solenoids aprinting condition signal in the form of an electrical voltageapproximately equal to that of the source 61 or alternatively a feedingcondition signal which is the absence of electrical voltage at thesolenoids. Consequently, during the feeding mode, valves 41 and 47 wouldbe left in their respective normally open and closed states, whereasduring the printing mode the signal voltage applied to their solenoidswill cause valve 41 to close, thereby cutting off vacuum to plenumchamber 24, and valve 47 to open, thereby applying the full vacuum ofsource 49 to plenum chamber 25.

The same information as to the operating mode of the printing apparatusllt) can be derived by monitoring the state of motion of the belt ill,since in the apparatus the movements of belt it and printing head 14 arecoordinated by suitable means not shown and not forming a part of thisinvention. To control the operation of valves 41 and 47 on the basisofinformation derived from the movement of belt 11, a switch 60A, (shownin phantom) can be substituted for the switch 60 in the same electricalcircuit that includes switch 60, voltage source 6i and the operatingsolenoids of valves 41 and 47. Switch 60A is connected to or otherwisearranged in relation to belt ll so that when belt 11 is stopped, switch60A closes, and whenever belt ll is moving, switch 60A is open. In thisway,

the same basic types of feeding and printing condition indicator signalswill be established for operation of valves 41 and 47 as in the caseofthe printing head 14 monitoring switch 60.

As can be appreciated by the artisan other vacuum control arrangementscan be substituted for those described and illustrated herein providedthat the essential objectives of the invention are fulfilled. Theseobjectives are basically to control the vacuum pressure levels of plenumchambers 24 and Z5, and hence the vacuum gripping forces established bytheir corresponding grooves 30A and 30B in accordance with the operatingmode of the printing apparatus 10 such that during the feeding mode,both the set of grooves 30A in the feed station l2 to printing station13 belt area, and the set of grooves 30B in the printing area 31 are ata uniform vacuum pressure level that is less than the full vacuumcapability of the vacuum source 49, and during the printing mode, thevacuum to the set of grooves EltlA is cut-off while the full vacuumavailable from source 49 is applied to the set of grooves 308. Theuniform vacuum pressure level that is applied to grooves 30A and 308during the feeding mode can of course be made adjustable simply bychoosing a bleeder valve 48 having an adjustable vacuum regulatingmeans, or by substituting another bleeder valve 48 that will give thevacuum pressure level desired.

While in accordance with the provisions of the statutes there isillustrated and described herein a specific embodiment of the invention,those skilled in the art will understand that changes may be in the formof the invention covered by the claims, and that certain features of theinvention may sometimes be used to advantage without a corresponding useofthe other features.

We claim:

1. ln a printing apparatus wherein sheet material to be printed isconveyed along a given path by a porous belt from a feed station to aprinting station and thence to a collection station, with the printingoperation being performed at the printing station by a printing headwhich is moveable relative to the belt, a vacuum table system whichcomprises a vacuum table positioned for contact with the inner side ofsaid belt to support same along the path of conveyance, said vacuumtable having partition means defining a plurality of evacuable spacesopen to the inner side of the belt to establish corresponding suctionareas along the outer side of the belt for gripping the sheet materialconveyed thereby, said plurality of evacuable spaces including a firstgroup of evacuable spaces establishing suction areas located betweensaid feed station and said printing station, and a second group ofevacuable spaces establishing suction areas located at said printingstation and between said printing station and collection station, andmeans communicating the spaces of each group with one another toaccommodate evacuation of all spaces in one group to a given pressureindependently of the pressure to which the spaces of the other group areevacuated, whereby the gripping force exerted on the sheet materialconveyed through the suction areas associated with said spaces can beadjusted by correspondingly adjusting the evacuation pressures of saidfirst and second groups of spaces.

2. A vacuum table system according to claim ll including a vacuumsource, and control means communicating with said vacuum source andcommunicating with said first and second groups of evacuable spaces,said control means being operable to selectively communicate said firstgroup of spaces with said vacuum source and establish a predeterminedevacuation pressure throughout the suction areas associated with saidfirst group of spaces, and operable to selectively communicate saidsecond group of spaces with said vacuum source and establish apredetermined evacuation pressure throughout the suction areasassociated with said second group of spaces.

3. A vacuum table system according to claim 2 wherein said control meansincludes monitoring means responsive to the condition of said printingapparatus to establish a printing condition indicator signal wheneversaid apparatus is in a con dition for immediately performing a printingoperation upon sheet material at the printing station, and vacuum levelregulation means operable to increase the evacuation pressure level ofsaid second group of spaces in response to said indicator signal,whereby during the printing operation the gripping force on the sheetmaterial at the printing station is increased.

4. A vacuum table system according to claim 3 wherein said monitoringmeans senses the position of said printing head and establishes theprinting condition indicator signal whenever the printing head is in theposition it normally assumes when performing the printing operation.

5. A vacuum table system according to claim 3 wherein said monitoringmeans senses the state of motion of said belt and establishes theprinting condition indicator signal whenever the belt is in the state ofmotion it normally assumes during performance of the printing operation.

6. A vacuum table system according to claim 2 wherein said control meansincludes monitoring means responsive to the operating condition of saidprinting apparatus to establish a printing condition indicator signalwhenever the apparatus is in its printing mode of operation, and toestablish a feeding condition indicator signal whenever the apparatus isin its feeding mode of operation, and vacuum level regulation meansoperable in response to said feeding condition indicator signal toestablish a first uniform evacuation pressure level in said first groupof spaces and also in said second group of spaces, said vacuum levelregulation means being operable in response to said printing conditionindicator signal to establish an atmospheric pressure level in saidfirst group of spaces, and a second evacuation pressure level in saidsecond group of spaces, said second evacuation pressure level beinghigher than said first evacuation pressure level, whereby during thefeeding mode of operation a uniform gripping force corresponding to saidfirst evacuation pressure is applied to sheet material conveyed from thefeed station to the printing station, and to sheet material conveyedfrom the printing station toward the collection station, and during theprinting mode of operation the gripping force applied to sheet materialat the feed station is reduced to approximately zero while the grippingforce applied to sheet material at the printing station corresponds tosaid second evacuation pressure level.

7. A vacuum table system according to claim 6 wherein said control meansincludes a vacuum source, a bleeder valve, a first control valve and asecond control valve both operable in response to said feeding andprinting condition indicator signals, said first and second controlvalves and said bleeder valve being interconnected to define a vacuumlevel regulation circuit communicating with said first group of spaces,with said second group of spaces, and with said vacuum source, saidfirst and second control valves being responsive to said feedingcondition indicator signal to establish in said regulation circuit anevacuation pressure equalizing flow connection between said first andsecond groups of spaces and to establish a flow connection through saidbleeder valve between said vacuum source and both groups of said spacesto maintain a common evacuation pressure therein determined by thebleeder valve, said first and second control valves being responsive tosaid printing condition indicator signal to establish in said regulationcircuit a flow connection between said second group of spaces and saidvacuum source.

8. A vacuum table system according to claim 7 wherein one of said firstand second control valves is responsive to said printing conditionindicator signal to vent said first group of spaces to the ambientatmosphere.

9. A vacuum table system according to claim 1 wherein said vacuum tablecomprises a plate having a first set of spaced apart grooves definingsaid first group of evacuable spaces, and having a second set of spacedapart grooves defining said second group of evacuable spaces; a firstplenum chamber adjoining said plate in underlying relation to said firstset of grooves; a second plenum chamber adjoining said plate inunderlying relation to said second set of grooves; passage meansextending through said plate to communicate said first set of grooveswith said first plenum chamber; and passage means extending through saidplate to communicate said second set of grooves with said second plenumchamber, both said first and second plenum chambers being evacuableindependently of each other for establishing corresponding evacuationpressures in the spaces defined by their respectively associated sets ofgrooves.

